Classification of laser welding

1, According to control methods, it can be divided into manual laser welding machines, automatic laser welding machines, and galvanometer laser welding machines
2, According to lasers, they can be divided into: YAG laser welding machine, semiconductor laser welding machine, and fiber laser welding.
There are two basic modes of laser welding: laser thermal conductivity welding and laser deep penetration welding. The former uses a lower laser power density (105-106W/cm2). After the workpiece absorbs the laser, it only achieves surface melting, and then relies on heat transfer to guide the internal heat transfer of the workpiece to form a molten pool. This welding mode has a shallow fusion depth and a relatively small depth width. The latter has a high laser power density (106-107W/cm2), and the workpiece quickly melts and even vaporizes after absorbing the laser. The melted metal forms a small hole under the action of steam pressure, and the laser beam can directly shine on the bottom of the hole, making the small hole continuously extend until the steam pressure inside the hole is balanced with the surface tension and gravity of the liquid metal. When the small hole moves along the welding direction with the laser beam, the molten metal in front of the small hole flows around the small hole towards the rear, solidifying and forming a weld seam. This welding mode has a deep penetration and a large aspect ratio. In the field of mechanical manufacturing, except for those thin parts, deep penetration welding should generally be used.
The metal vapor and protective gas generated during deep penetration welding undergo ionization under the action of laser, thereby forming plasma inside and above the small hole. Plasma has absorption, refraction, and scattering effects on laser, so generally speaking, the plasma above the molten pool will weaken the laser energy reaching the workpiece. And it affects the focusing effect of the beam and is detrimental to welding. Usually, side blowing can be added to expel or weaken the plasma. The formation of small holes and plasma effects result in the generation of characteristic sound, light, and charge during the welding process. Studying their relationship with welding specifications and weld quality, and using these characteristic signals to monitor the laser welding process and quality, has significant theoretical significance and practical value.